I have a series of obfuscated strings which across the set of strings have regions of high variance and regions of low variance – implying some encoding mechanism as opposed to an encryption procedure ...

Recently, a new cipher called Spritz has been released by Ronald L. Rivest and Jacob Schuldt. It should be a "drop-in replacement" for RC4.
There are many differences to RC4, Spritz is "spongy" and ...

I came across some source code that loosely does the below in order to achieve a 32 bit hash.
The input string is passed through MD5 to get 16 bytes Hash (as usual). Then the 16 bytes are split into ...

The standard security property demanded of a blockcipher is that it be a pseudo-random permutation; i.e., given a uniformly random key, the blockcipher should be computationally indistinguishable from ...

I was learning about the finding the key length reading the following web site...
http://practicalcryptography.com/cryptanalysis/stochastic-searching/cryptanalysis-vigenere-cipher/
and I really don't ...

So, I have been assigned an assignment where I had to solve a Vigenere cipher.
Following along with this webpage I managed to get all the way to the chi-squared step. But, that is the problem. Upon ...

Fully homomorphic encryption schemes allow one to evaluate any arbitrary computation over encrypted data. Intuitively this seems to be too weak, irrespective of how we achieve this.
An adversary who ...

(Crypto Gods, I should begin by stressing that I haven't lost my mind: I'm not doing this in real life, I'm just trying to understand the theory behind what's happening. With your help, hopefully I ...

Recently, I was given three ciphers to crack for my cryptography class. At this point, I have guessed that one of them is likely a Hill cipher (probably 3x3, as that is the most complex we have done ...

Suppose a $1000$-bit key used in the one-time pad is not randomly and uniformly generated.
Suppose that the values of the first $5$ bits are $0$, and the other $995$ bits are randomly generated and ...

I am currently reading about PBKDF2, and understand that the salt is used only once, while the password is used multiple times in the computation of the final key (see this question). How would the ...

I have just found a way to crack AES-128 in a reasonable time (1-2 days). How do I publish and prove this? I remember reading about lots of people who cracked DES and other ciphers but how did they ...

In general (if possible to determine) which would make an output harder to turn into plain text with a computer?
Extreme Length (minor complexity change)
Extreme algorithmic complexity (minor length ...

I am trying to derive a symmetric key based on a master key, combined with a simple string. Based on my limited knowledge, it seems that something like PBKDF2 would do that for me in a well-defined ...

Say I have some black box which, given any English word, deterministically outputs a token for that word. Assume our black box is implemented using strong cryptography, i.e. the hardness of reversing ...

I'm brainstorming some different ways of making deterministic encryption more secure. I want to use deterministic encryption to preserve searchability over the keywords in a document set. However, I ...

I am new in cryptography. I want to determine the complexity of revealing a random bit permutation which is used as block cipher for plaintexts (bitstrings of length n). An adversary catches different ...

The high security of RSA is granted, because it is very hard to factorize
$$
N = p * q
$$
Nevertheless, there is actually no need of factorizing $N$, in order to generate the $Private$ $Key$, but the ...

The simplest way to generate truly random numbers for OTP keys is to measure the time in milliseconds between each keystroke on a keyboard. The randomness depends on the user typing in various speeds. ...

I have some spare time, and a few hundred DJB2-hashed values sitting around. I thought I'd try to do something "useful" and invert DJB2, such that I could calculate the plaintext of the hashes (which ...

Consider the function $F$ from $\{0,1\}^{56}$ to $\{0,1\}^{64}$, mapping the operative bits of a DES key to the ciphertext for all-zero plaintext. How could we organize a rainbow table to invert that ...

I'm working with a third party protocol which employs AES-128 in ECB mode of operation to encrypt a packet composed of 16-byte blocks (it encrypts each block independently). I'm trying to determine if ...

I see that Lagrange interpolation is commonly used for secret sharing, but could it be used for encryption?
The goal is to reduce database I/O and compute new values on the fly. Suppose the use case ...

Say I'm trying to brute force the original plain text of an SHA256 hash, does knowing the RIPEMD160 hash of the same text help? In other words, does providing access to hash values of the same text ...

This may seem an elementary question about LFSRs, and their link to Markov chains. LFSRs show Markov chain behaviour in that there can be a transition matrix defined over the LFSR, this follows from ...

If an attackers sets out to crack the symmetric key of e.g. AES-CTR, would they prefer to have access to many small cryptotexts or one large cryptotext? I.e. is it more interesting for the attacker to ...